That’s always my first answer indeed. "Well, I’m going to answer your question but first, just think about the abolition of legal slavery a while ago. What would you have thought about someone who would object : “yeah, but what will we replace slavery with ?”.
Well, I can try to clarify here. Some prison abolitionist, activist or scholars, do indeed think there will be a residual proportion on crime that will necessitate kind of spatial segregationi, and, for some, being locked up for a time.
And it’s not necessarily conflicting with the abolitionist motto. They say : Well, prisons are buildings, but mostly, they are a social and historical function (punishing the poor, the political opposition, etc.). If we abolish that and there are like 3000 people in prison nationwide, the logic of stockpiling inmates will be gone. Maybe it will be possible to actually do something for them. The gap in punishment between the poor and the rich will be reduced if not gone.
Nevermind the building. If their historical function is gone, prisons are gone.